Hit By Lightning

[cabinetman]

Had lunch with some friends and we were comparing notes on surge protection and battery back-up. They own a 4 unit building in Maine that was hit on one side by lightning. He said outlets in the building got smoked and burnt until the breakers threw. Other damage was a large hole blown out on the inside of the building, on an interior wall.

What had me wondering is he said it killed all phone lines and blew the phone receptacle out of the wall. I thought a certain wire size could only carry so much voltage/amps. That phone wire is like 22 or 24 ga , that's ity bity. Wouldn't that wire disintegrate before the surge got into the building?
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[Tom Slick]

my guess would be that at the ultra high voltage lightning is at it doesn't need conductors, so that tiny phone line provides just a little easier path for a microsecond. once ionization happens the energy is flowing with or without a conductor.

[smorris]

The lightning would blow those fine wires into plasma which is a very good conductor.

We were on our boat in the cabin when it go hit the first time and it was quite the light show with blue light running in rivers across almost every surface. Some things that blew out made perfect sense like all the electronics. The copper bottom paint blowing off in a big sheet was a surprise. The bilge alarm pointed out that we had also melted 2 thruhulls at the waterline.

[LCHIEN]

there are only two things that truly limit the amount of current that a wire can handle and they are the resistance/corresponding voltage (e.g. ohms law) and the heat dissipated.

Lightning has both an amazing amount of current available and hundreds of thousands of volts to push it - the next thing is the heat, with all that current coursing thru it it will melt quickly but as Tom S says, it vaporizes and the current follows the ionized paths regardless.

what you think of as rules for what current wires can carry is safe design rules.
The NFPA (nat'l fire protection assn) issues rules on what wires are allowed to carry what amps, and that is so the wiring remains safe (mostly from overhating and causing fires. Home builders, electricians and designers are wise to follow those rules but Lightning does not. As an engineer, we follow NFPA rules for user safety, but also have a bunch of other rules to follow that affect wire size and choice, such as equipment requirements and performance.

When lightning hits there's so much current flowing pushed by thousands of volts that it splits like a flooding river takes all kinds of pathways imaginable.

[Uncle Cracker]

I've seen lightning blow just the top 3" off a thousand feet of 8" sprinkler pipe buried in the ground. It is so powerful that it is simply unpredictable. It is simply looking for a way to ground, and when it hits a structure, it's likely to take practically any (and often all) possible routes... It also moves fast, so it's already got to the end of a small wire and done it's damage before any portion of the wire has time to blow up and interrupt it.